The invention relates to a breathing apparatus and more particularly to a self-contained portable breathing apparatus for temporary use by a wearer in a noxious or oxygen-deficient atmosphere. Such apparatus are worn by fire fighters or industrial workers when exposed to smoke, oxygen deficiency or noxious gases. Portable breathing apparatus of this kind are generally of the open circuit type.
In the typical open circuit breathing device, compressed breathing gas is delivered to the wearer and the expired gases are vented to the atmosphere. The compressed breathing gas is stored in a cylinder which is attached to a harness assembly on the wearer's back.
The breathing gas is reduced to a low, breathable pressure in a two stage process. A first stage pressure regulator reduces the cylinder breathing gas and delivers it to the second stage demand regulator. The demand regulator reduces the breathing gas pressure to near atmospheric and delivers it to the face mask to meet the demand of the user.
In such breathing apparatus, manually operated override valves sometimes referred to as "by-pass" controls are often used to safeguard against a failure in the closed position of the first stage pressure reducer or second stage demand regulator. Such a failure without a "by-pass" control device would prevent breathing gas from being delivered to the user's face mask.
Typically, prior breathing systems feature a face mask which is uncomfortable and cumbersome to the wearer, and while some of the more modern systems have utilized a helmet with a face mask the methods for sealing the face to the mask have attendant disadvantages. While some types of helmets provide inflatable devices of various designs for sizing the helmet and cushioning an impact, the present invention provides the novelty of an integral pneumatic pump and valving mechanism obviating the need for an external compressed gas source.